﻿#/usr/bin/python3
# -*- coding: utf-8 -*-
        
def main():
    dic = {}
    dic['a'] = 1
    if 1==dic['a']:
        print(1)
    # 判断 key 是否存在，注释方法报错，应该用下述方法
    # if dic['b'] is None:
    #     print('null')
    if 'b' in dic.keys():
        print('b')


if __name__ == "__main__":
    main()